This invention relates to a method for producing a mixture containing cycloalkanones and/or cycloalkanols which comprises oxidizing a cycloalkane with molecular oxygen to a cycloalkyl hydroperoxide and decomposing the cycloalkyl hydroperoxide.
The oxidation reaction of a cycloalkane with molecular oxygen generally belongs to an autoxidation reaction and comprises the stage where a cycloalkyl hydroperoxide is produced from a cycloalkane and molecular oxygen and the stage where said cycloalkyl hydroperoxide decomposes to produce a cycloalkane and a cycloalkanol. The reaction of the first stage proceeds with relatively high yields while in the reaction of the second stage the decomposition degree of the cycloalkyl hydroperoxide differs greatly depending on the catalysts present in the system.
Hitherto, decomposition of cycloalkyl hydroperoxides has been effected in the presence of metallic salts. For example, "Kogyo Kagaku Zasshi" 73, 2056 (1970) reports the decomposition of cyclohexyl hydroperoxide with cobalt oxide, but this is not necessarily satisfactory because catalysts in high concentrations of several thousands ppm must be used to obtain sufficiently high decomposition rates.
Furthermore, "Kogyo Kagaku Zasshi", 73, 2388 (1970) reports the decomposition of cyclohexyl hydroperoxide with cobalt naphthenate, etc. However, this requires the high decomposition temperature of 160.degree. C. in spite of using a high catalyst concentration of 10 ppm.
U.S. application No. 187719 discloses the decomposition of cyclohexyl hydroperoxide with bis(pyridylimino)isoindoline complexes of cobalt and the like. However, according to this method the ratio of the resultant cyclohexanone and cyclohexanol is small, namely, about 0.2 and selectivity to cyclohexanone is low. Industrially, the mixtures of cyclohexanone and cyclohexanol are used mainly as starting materials for .epsilon.-caprolactam and adipic acid. Production of .epsilon.-caprolactam requires cyclohexanone and thus the step of dehydrogenation of cyclohexanol to cyclohexanone is necessary. Therefore, the higher production ratio of cyclohexanone is desired. When the mixture is used for production of adipic acid, the yield of adipic acid is maximum in the case of the ratio of cyclohexanone and cyclohexanol being 0.67 according to U.S. Pat. No. 3,987,100. Thus, the higher production ratio of cyclohexanone is desired. That is, the higher production ratio is desired in decomposition of cyclohexyl hydroperoxide.
The inventors have made intensive researches on the method for producing a cycloalkanone and a cycloalkanol by decomposing a cycloalkyl hydroperoxide where decomposition rate of cycloalkyl hydroperoxide is high, yields of cycloalkanone and cycloalkanol are high, and the production ratio of cycloalkanone is high, and as a result this invention has been attained.